May 4, 2013

When I got pregnant, I was diagnosed with viral hepatitis — more specifically, the doctor said I am a hepatitis B carrier. What does that really mean? I don’t have any symptoms as far as I know. Both my kids and my husband have been vaccinated. But what do I have to do for myself? Do I have to be vaccinated? I am a bit worried about this and I would appreciate it if you can enlighten me regarding this query.

In the United States, we usually think of hepatitis B as a sexually transmitted disease, and of course it can be spread in that way. But, if we look at hepatitis B from a world-wide perspective, the commonest form of transmission is probably from infected mother to newborn child. Therefore, it is now the standard of care to test all expectant mothers for this virus, so that their newborns can be promptly treated to prevent such transmission. Many women, like you, are surprised to learn that they are hepatitis B carriers, which means that they are chronically infected with the virus.

There are a number of blood tests done to evaluate hepatitis B, and they can be useful in determining the stage of infection and how much risk there is of transmission from someone who is infected to someone else, either sexually or to a newborn at birth. These tests measure various antigens, which are parts of the actual hepatitis virus itself, and the antibodies that our bodies produce against those antigens when we are infected or vaccinated.

Three hepatitis B antigens are recognized: the surface (s) antigen, the core (c) antigen, and the e antigen. The s and e antigens can appear in the blood, and are commonly tested for. The c antigen remains in liver cells, and there is not a commonly used clinical test for it. The tests for the s and e antigens are usually noted as HBsAg, and HBeAg.

Each of the antigens has a corresponding antibody, and clinical tests for all three are commonly done. These are the HBsAb, the HBcAb, and the HBeAb. (Ab is short for antibody, Ag for antigen). A complete panel of hepatitis B tests therefore consists of HBsAg, HBsAb, HBcAb, HBeAg and HBeAb. They are reported as positive or negative, not as numbers. So what do they mean?

When a person if first infected with the virus, HBsAg and HBeAg appear in the blood. These indicate that the virus is duplicating itself in the body and is present in the blood. A short while later the HBcAb appears. This is simply the body’s response to the core antigen, and doesn’t tell us anything about how severe the infection is or whether it will become chronic. If the infected person is able to fight off the virus, which happens in about 95 percent of infected adults, the HBeAg disappears after about four months, and is replaced by the HBeAb. Slightly later HBsAg disappears and is replaced by HBsAb. The presence of HBsAb means that the immune system has successfully fought off the infection, and the person is not able to transmit the infection to others (although blood banks will never accept that person as a donor regardless).

If HBsAg has not converted to HBsAb by six months, then the person is said to have chronic hepatitis, meaning that the virus is still infecting the liver. If HBeAg has not converted to HBeAb, then the person is considered to be highly infectious. A woman who is HBeAg positive when she gives birth has a 90 percent likelihood of infecting her newborn if the baby is not quickly treated. If she is HBsAg positive but has converted to HBeAb — meaning that she is less infectious — the chances of her infecting her newborn fall to about 10 percent.

You apparently didn’t know that you were a carrier until this pregnancy, so possibly you had your first two children before the testing of expectant women was a routine practice. The fact they both escaped being infected means that you are probably in the HBsAg positive, HBeAg negative category, with a low risk of transmission.

Your husband and both children have been vaccinated. This is of course crucial for your husband to prevent sexual transmission to him, and is now standard pediatric practice for all children to prevent them catching the disease sexually when they grow up. Vaccination is done with the HBsAg particle, produced by recombinant technology that ensures that no other viruses are in the vaccine. Someone who has been vaccinated should become HBsAb positive. The absence of HBcAb in people who have been vaccinated distinguishes them from someone who has had the infection and recovered from it.

Vaccination would be pointless for you, since you are already chronically infected. There is treatment now for chronic hepatitis B, with interferon and a drug called lamivudine. Whether you would benefit from such treatment would depend on the age when you were infected (people infected as infants generally cannot be cured) and the state of your liver as determined by blood tests and a liver biopsy. After you are through with this pregnancy, you should be evaluated for treatment by a gastroenterologist. Your baby should be promptly treated after delivery, even though your first two children did not get infected, just on the off chance that he or she might fall in that 10 percent group.